Though a common method for controlling distance on pitch shots is to adjust the length of one's backswing, David Leadbetter advocates a primary focus on acceleration. "Instead of worrying about varying backswing lengths, focus on one length -- halfway back, with the left arm parallel with the ground. From there, key on the acceleration factor through impact. For example, if you want to hit a 90-yard shot, think about making a 90-mph swing. If you want to hit it 70 yards, make it 70 mph and so on. Obviously, these speeds are not accurate, but it's a great mental concept for improving distance control based on your pitch shots."More:
Hit The Gas To Improve Pitching Accuracy, by David Leadbetter